Can you check your php-apache.ini and php-cli.ini? Concerning magic_quotes they should look like this:

magic_quotes_gpc = Off
magic_quotes_runtime = Off
magic_quotes_sybase = Off

Should you not be able to fix the magic quotes settings directly in there (for instance due to no access to the two files), you can adjust/add these settings in a file called drush.ini, residing in your user's directory ('/home/your-user'). You can configure Drush far more -- see Drush's README.txt for more details.

I am trying to install spark-8.x-1.0-alpha8-core.zip [downloaded on May 22] on a Mac OS X (10.7.5). Everything was fine until 95% of the way through the "Installation profile" step of "Installing Spark". The progress bar shows 95% and the messages displayed are:

Installing Spark
Completed 39 of 41.
Installed Toolbar module.

Unfortunately I'm new to Drupal so I'm not sure what log files might be relevant, though I have looked mightily.

Some other potentially relevant details are appended. Thanks for your help.

I got the same problem.
Using Virtualbox with Fedora 18 distribution and mySQL
Fedora home is /var/www/html. I created a subdir drupal here.
PHP 5.4.15
If using the browser back button it seems to work but then all adminstration menus are not there (404).

Symfony\Component\Routing\Exception\RouteNotFoundException: Route "field_ui.display_overview.node.search_index" does not exist. in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 146 of /Applications/MAMP/htdocs/Testing/spark-8.x/core/lib/Drupal/Core/Routing/RouteProvider.php).